Laminated safety glass



' J. D. RYAN n LAMINATED vSAFETY lGLASS sept. 11, y1951 Filed June 15, 1947 Gttorneg @Ze/a OQ. 32u00; gygse fd Patented Sept. 11, 1951 LAMJNATED SAFETY GLASS Joseph D. Ryan, Toledo, Ohio, assigner to Libbey- Owens-Ford Glass Company, Toledo, Ohio, a

corporation of Ohio Application June 13, 1947, Serial No. 754,355

2 Claims. (Cl. 154-217) The present invention relates to laminated safety glass. More particularly, it has todo with laminated safety glass in which the plastic interlayer extends beyond the edges of the glass sheets to provide a flexible mounting and sealing ange, and contemplates a special type of interlayer for such structure.

Generally speaking. units of this general type y consist of two or more transparent panels, which may be sheets of glass, or other relatively hard transparent material, and an interposed layer or layers of a softer thermoplastic material, all bonded together under heat and pressure to form a composite wh'ole. 'I'he plastic interlayeris of sufficient area to extend outwardly beyond the.

edges of the glass sheets and form a plastic flange. which can be clamped betweenthe opposite members of the frame of a window or sight opening in a manner to seal the opening'and to provide a. flexible or iloating" mounting for the outer transparent panels of the unit.

' Although usable for any one of a number of different purposes, this typeV of glazing unit is especially well adapted for glazing the sight openings of aircraft, where protectiverequirements are unusually stringent and where a flexible type of window'mounting is especially desirable.

When such extended plastic type of unit is mounted in the window of an airplane, the plastic attaching `flange will provide a sort of sealing gasket which, when clamped inthe window frame, will completely and effectively lseal the window opening. This feature is particularly important in pressurized cabins and in high altitude or stratosphere flying. At the same time, the flexible attaching or mounting ange will aiord a certain `resiliency or freedom of movement of the glass-plastic structure relative tothe supporting frame in which it is mounted. In this way, the torsion and shock to which the aircraft is normally subjected will be cushioned and not transmitted directly to the glass, with the result that the tendency of the glazing unit tobe cracked or shattered from such causes will be greatly reduced if not entirely eliminated. Moreover, the twisting and weaving. and the varying pressure diierentialsv to which a plane is subjected, will not be `as apt `to break the glassv of a .unit vmounted in this manner, because of the ability of the unit to float in its mounting, without the introduction of localized strains. i

Another advantage of these units is that theyv These general advantages 'may be said-to be present in all of the conventional forms of extended plastic, laminated safetyv glass. But difficulties have been experienced in arriving at the proper type of plastic interlayer to give a unit that will be completely satisfactory under all possible conditions, especially in cases where these units, are called upon to perform services at extremely low temperatures. ForA instance. plastic interlayers of a softness suitable for general automotive work are so soft as to be unsuitable for extended plastic laminations under severe strain conditions. because of their high extensibility and insuicient tensile strength. 'I'his is because a highly extensible plastic attaching flange leads to excessive bellows action when mountedl in a plane, resulting in failure of the unit, particularly in pressurized cabins.

On the other hand,- theuse of plasticv interlayers that are hard enough to give the necessary tensile strength vand resistence to bellows action, when used at very low temperatures. for example at.-75 Fahrenheit which is specified for y B-29 closures, results in the spalling of the glass in the unit. This spalling of the glass generally.

occurs'aroundfthe edges of the lamination and in many ca ses extends well into the visiony area with consequent obscuring of vision and weak'- ening ofthe glazing structure.

Now I have discovered that unit in which the plastic interlayer is composed material.

Broadly` stated, it is the primary aim of the.

present invention to provide a new kind.` of extended plastic type laminated safety glass unitA which will be stable over an extremely wide range of temperatures; which will havev low extensibility under load, andv high tensile strength vover the entire range; and in Whichtheglass will not spall even atl temperatures of -'7V5""Fahrenheit and lower', `1

A more speciiic object is the provision of an i extended plastic type of r`laminated glassin which j, the plastic interlayer is made v.up ofr arelativelyA thick central Acore ofa Arelatively.-hard vrlastic vfaced with thinner layers of a relatively'soft plas Still another object isto provide an extended plastic unit of this character inV which there is no bead or collar of plastic around the edgesl of the glass sheets. f

Other objects and advantages will become morev apparent during the course of these-,objectionable features. can be overcome by the provision `of an o extended plastic type of laminated safety glass` vof the invention I :,sozass the following description. when taken in emnection with the accompanying drawings.

In the drawings, wherein like numerak are employed to designate like parts throughout the same:

Fig. '1 is a fragmentary view of the side of an airplane showing a sight opening gland with the extended plastic type laminated safety glas lmlt of this invention; y

Fig.2isasectiontakensubstantlallyalongthe line 2-2 in Fig. 1;

Fig. 3 is an enlarged fragmentary sectional view of one side of the unit of Fig. 2; and

Fig.4isaviewsimilartoldg.3,showingthe objectionable plastic bead or collar that may sometimes be found during production of the unit, and a metal reinforcing member in the plastic interlayer.

Referring now more particularly to the drawings, the laminated structure l shown there includes two sheets of glas Il and II, and an in terposed central sheet of thermoplastic material designated in its entirety by the numeral l2, all bonded together into a unitary structure.

The glasssheets Il and II maybeofordinary plate or sheet glas, or may be fully or semitempered glass. or any combination of known types of glas sheets or plates. 'Ihe cenhal sheet I2 is preferably made up of a thick central core of relatively hard plastic I3, and two thinner layers of relatively soft plastic Il. The several strata of the plastic central sheet may be formed of a polyvinyl acetal resin, for example, polyvinyl butyral resin plasticized with a suitable plasticizer such as dibutyl sebacate, triethylene glycol dihexoate or triethylene glycol ester of the fatty acids from cocoanut oil ranging in' rbon content from C@ to Cs.

Excellent results are obtained when the oentral core: I3 .is polyvinyl butyral plasticized with 21 partsA plasticizer per 100 parts of the resin by weight, and the facing layers I4 ane polyvinyl butyral plasticized with 37% parts plasticizer per 100 parts of the resin by weight.

Ascanbeplainlyseeninli'igs.2and3,in producing the safety glass units, a central plastic sheet I2 is employed that is oflarger area than the glas sheets so that in the finished unit the plastic interlayer extends outwardly beyond the glas sheets at all four edges to provide the plastic attaching flange I5. flange, the laminated glazing unit l can be flexibly but permanently mounted in a sieht opening I6 of an aircraft I1.

This can be done, for example, by clamping the extended plastic attaching flange I5 between the skin Il of the ship, forming one side of the window frame, and a collar or movable frame portion Il, with machine screws or the like 20. The glas sheets Il and Il are preferably spaced slightly from the frame as at 2| to allow the glas portion of the unit to "float" in the frame within the limits of the exlbility of the attaching flange.

In the unit shown in Figs. 2 and 3, the extended plastic flange It is used without reinforcement of any kind. However, when dired, a metal reinforcing member, shown at 22 in Fig. 4, may be employed. This reinforcing member is preferably in the form of an aluminum or other metal collar or frame, about .02o to .030 of an inch thick, that is embedded in the plastic interlayer around the marginal portions thereof. Formerly, it was believed that such reinforcing meanscontributedtothedlllcultielthltm By means of this' 4 hadwithspallingoftheklassatlowtmnerltures. But with the special laminated plastic interlayer of this invention, the metal reinforcing imertscanbeusedwhencverdesiredwithoutbad effect.

Another important feature of the invention lieslnthefaetthatnoprtoi'theplastieinterlayerispermittedtoadheretotheedgesoftlm glass. In manufacturing the umts, the several laminations are together in proper superimposed relationship and then prepressed under relatively slight heat and light pressure toremoveairfrombetweenthelaminationsand tocausethemtoadheretooneanother. The prepresing is generally carried out either by placing the assembli in a plastic bag and exhaustingtheairfromthebagorbyprsing the assembled laminations between the platens of a press. This prepressing is then followed by afinalpressingorcompositing,usuallylnanoll autoclave at around 50 pounds pressure per squareinchandatemperatureofaround250' Fahrenheit.

I During these prelimimry and final pressing treahnents the thermoplastic interlayer may flow, or be pressed, outwardly from between the glass sheets to form a plastic bead, collar or fillet, illustrated at 22 in Hg. 3, which adheres tightlytotheedgoftheglassatu. Ihave discovered that, if this plastic fillet is allowed to remain, it becomes a major contributing factor to spalling of the glass edges when the unit is put into use at low temperatures.

This is probably due to the fact that the adhesive forces set up between the overlying plasticandtheglassedgesareveryhighandthe difference in the coefficient of expansion between the glass and plastic is such that the plastic shrinks Ain the cold approximately ten times as f ast as does'the glas. Consequently, at extremely low temperatures, the plastic fillet 2l will literally pull pieces oil of the edges of the glassheetsandsodlssuretheunitbythisglass spalling.

In my construction, I overcome this condition either by routing out and removing the plastic fillet 2l after the unit is composited, or by coniining the plastic interlayer during the pressure treatment so that it will be unable to dow out from between the glas sheets or into contact with the glass edges.

Some variation in the thicknss of the several layers of the central plastic sheet I2 is permissible depending on the type of installation in which it is'to be employed and the load to be carried, but a typical recommended structure which has proved very satisfactory in the glazing of B-29s is as follows:

area. Layer of glass.

The relatively thin layers Il of the central plastic sheet I2 may be of sumcient area. to extend outwardly from the glass sheets and eom. pletclyennrtheelatnloolllllldlllnd, But

in most cases I prefer to employ this softer plastic only within the area of the glass vas shown, since the use of the more highly plasticized material on the extended flange I5 tends to increase its tackiness, which is disadvantageous.

Extended plastic, laminated safety glass units of the character shown and described here, and constructed in the manner outlined can be used in such extreme conditions as in glazing high altitude planes, or observation openings in refrigerated wind tunnels, where temperature ranges from approximately '80 Fahrenheit to +150 Fahrenheit may be encountered, and these units will not only remain perfectly stable but will adequately resist glass spalling.

It is to be understood that the form of the in vention herewith shown and described is to be taken as a preferred embodiment of the same, but that various changes in the shape, size and arrangement of parts may be resorted towithout departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. A laminated unit, comprising two sheets of glass and an interposed sheet of thermoplastic material bonded thereto to provide a unitary structure, said interposed sheet comprising a .095 inch thick layer of polyvinyl butyral resin plasticized with approximately 21 parts plasticizer per 100 parts resin by weight and two facing A layers of .015 inch thickpolyvinyl butyral resin plasticized with 371/2 parts of plasticizer per 100 parts resin by weight, said .095 inch thick layer being of suiilcient area to have portions thereof extending outwardly from between the transparent panels to provide a flexible attaching flange for the unit.

2. A laminated unit, comprising two sheets of structure, said interposed sheet comprising a .095 inch thick vlayer of polyvinyl butyral resin plasticized with approximately 21 parts plasticizer per 100 parts `resin by Weight and two facing layers of .015 inch thick polyvinyl butyral resin plasticized with 371/2 parts of plasticizer per 100 parts resin by weight, said .095 inch thick layer being of sulcient area yto have portions thereof extending outwardly from between the transparent panels tol provide a flexible attaching flange for the unit, but said .015 inch thick layers lying entirely within the area of said glass sheets, and said panels having their edges entirely free from contact with the plastic of said interposed sheet.

JOSEPH D. RYAN.

REFERENCES CITED The following references are of record in the file 'of this patent:

UNITED STATES PA'I'EN'rs 365,828 Great Britain Jan. 28, 1932 

1. A LAMINATED UNIT, COMPRISING TWO SHEETS OF GLASS AND AN INTERPOSED SHEET OF THERMOPLASTIC MATERIAL BONDED THERETO TO PROVIDE A UNITARY STRUCTURE, SAID INTERPOSED SHEET COMPRISING A .095 INCH THICK LAYER OF POLYVINYL BUTYRAL RESIN PLASTICIZED WITH APPROXIMATELY 21 PARTS PLASTICIZER PER 100 PARTS RESIN BY WEIGHT AND TWO FACING LAYERS OF .015 INCH THICK POLYVINYL BUTYRAL RESIN PLASTICIZED WITH 37 1/2 PARTS OF PLASTICIZER PER 100 PARTS RESIN BY WEIGHT, SAID .095 INCH THICK LAYER BEING OF SUFFICIENT AREA TO HAVE PORTIONS THEREOF EXTENDING OUTWARDLY FROM BETWEEN THE TRANSPARENT PANELS TO PROVIDE A FLEXIBLE ATTACHING FLANGE FOR THE UNIT. 